This May 14, 2014, image, provided by Denver International Airport, shows newly erected signs warning travelers about the danger of the MERS virus. / Denver International Airport via AP

by Elizabeth Weise, USATODAY

by Elizabeth Weise, USATODAY

Health officials report a possible third case of MERS in the United States, though the infected individual didn't get sick and was not hospitalized.

Middle East Respiratory Syndrome coronavirus (MERS) is new to humans and was first reported in Saudi Arabia in 2012.

The new case was discovered in an Illinois man who had contact with the nation's first MERS case, an Indiana man who contracted the virus in Saudi Arabia.

"We think that this patient was likely infected with MERS, but technically he doesn't count as an official case of MERS" because the World Health Organization doesn't list the antibody test the Centers for Disease Control and Prevention used to confirm it in the official description, said David Swerdlow, incident manager for MERS response activities at the CDC.

The Illinois man had two business meetings with the Indiana patient shortly before the Indiana patient was identified as having MERS, CDC officials said.

The longest of those meetings was for 40 minutes, said Swerdlow. It involved "face-to-face, close contact, within 6 feet, for over 30 to 40 minutes," said Swerdlow. The two men shook hands, he said.

The Illinois man is a U.S. citizen and has never traveled to the Arabian Peninsula. He might have reported a slight runny nose, but it wasn't clear whether that was related to the MERS infection, CDC said. He is reported to be feeling well now.

He is currently under "self isolation," said Swerdlow, in which he avoids contact with other people or wears a face mask.

Health officials have been testing everyone who had been in contact with the Illinois man.

Initial tests of the man, whom health officials are not naming, were negative.

But blood tests that came back late Friday night showed that the Illinois man had had a MERS infection, the CDC reported Saturday afternoon.

"These laboratory test results are preliminary and suggest that the Illinois resident probably got the virus from the Indiana patient and the person's body developed antibodies to fight the virus," the CDC said in a statement.

The Indiana man was the first case of the virus found in the United States. He is a health care worker who had traveled to Saudi Arabia.

Officials have not named him, either, but they say he was admitted to Community Hospital in Munster, Ind., on April 27 with a fever, cough and shortness of breath. It was confirmed that he had MERS on May 2. He has since fully recovered.

The nation's second confirmed imported case of MERS was reported in Florida on May 11.

Public health officials are reaching out to health care professionals, family members and others who had close contact with the two men to watch for possible infections.

News that someone could be infected with the MERS virus and yet remain healthy is welcome to health officials.

Previous reports made it seem as if the illness was always severe. It now appears "there is evidence that there is a broader spectrum of illness with MERS than was initially suspected, that there can be no symptoms," he said.

That could be because only those with severe cases have been tested for the virus up until now, said Swerdlow.

He emphasized that the investigation is ongoing and that health care workers are still trying to understand even basic information about the newly emerging disease, such as how it is transmitted.

Public health officials also are working with airlines to identify and notify U.S. travelers who may have been exposed to the patient on any flights.

As of May 16, there have been 572 laboratory-confirmed cases of MERS in 15 countries. Of those, 173 patients died.

Efforts are now under way to identify, notify, test and monitor close contacts of the Illinois resident.

To date, all reported cases of MERS have been linked to countries in and near the Arabian Peninsula.

MERS symptoms:

â?¢ Fever and pneumonia or acute respiratory distress syndrome

Risk factors:

â?¢ History of travel from countries in or near the Arabian Peninsula within 14 days before symptom onset

â?¢ Close contact with a symptomatic traveler who developed fever and acute respiratory illness (not necessarily pneumonia) within 14 days after traveling from countries in or near the Arabian Peninsula

â?¢ Close contact with a confirmed or probable case of MERS while the person was ill